Question

A voltmeter and an ammeter are connected in series to an ideal cell of emf E. The voltmeter reading is V and the ammeter reading is l

• A. V < E
• B. the voltmeter resistance is V/I
• C. the potential difference across the ammeter is (E-V)
• D. voltmeter resistance plus ammeter resistance $=E/I$

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A V < E
B the voltmeter resistance is V/I
C the potential difference across the ammeter is (E-V)
D voltmeter resistance plus ammeter resistance $=E/I$

All options are correct.
1) $V<E$ becuase there will be voltage drop across ammeter alse. If voltage across ammeter is $V_a$ then $E=V+V_a$.
2) Applying Ohm's Law across Voltmeter $V=I{R}_{voltmeter}\Rightarrow R_{voltmeter}=\frac{V}{I}$
3) As stated in 1st option explanation $E=V+V_a$
so, potential difference across ammeter is $V_a=E-V$
4) Since the cell is ideal, its internal resistance $r=0$, hence, by ohm's law, $R_{total}=\frac{E}{I}$